Fuel cell, control method for fuel cell, and computer readable recording medium

ABSTRACT

A fuel cell, a control method of the fuel cell, and a non-transitory computer readable recording medium recording a computer program capable of favorably generating power while suppressing leakage of gas and preventing the solenoid valve from being frozen with a simple configuration. The fuel cell includes a stack configure to generate electricity by reacting hydrogen and oxygen, an exhaust valve or a drain valve which is a solenoid valve discharging gas discharged from the stack to the outside, and a control unit configured to control energization of the exhaust valve. The exhaust valves are aligned in a gas discharging direction whereas the drain valves are aligned in a water discharging direction. If there is a risk of any solenoid valve being frozen, the control unit performs energization processing of energizing other solenoid valves in the state where at least one of the aligned solenoid valves is closed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 16/036,365, filed on Jul. 16, 2018, which is acontinuation of International Application No. PCT/JP2016/085349, filedon Nov. 29, 2016, which claims priority to Japanese Patent ApplicationNo. 2016-010035, filed on Jan. 21, 2016. The contents of theseapplications are incorporated herein by reference in their entirety.

FIELD

The present disclosure relates to: a fuel cell provided with a powergeneration unit configured to generate electricity by reacting hydrogenand oxygen, a solenoid valve for discharging gas or water emitted fromthe power generation unit to the outside, and a control unit configuredto control energization of the solenoid valve; a control method for afuel cell; and a non-transitory computer readable recording mediumrecording a computer program for causing a computer to executeprocessing of controlling gas discharge.

BACKGROUND

Examples of a battery cell which obtains electromotive force by sendinghydrogen to a negative electrode include a fuel cell, a nickel-hydrogencell and the like.

Since a fuel cell is a clean power generator having high powergeneration efficiency that may serve to construct a cogeneration systemwithout being affected by the magnitude of the load, it has beenconsidered to employ a fuel cell in various purposes including digitalhousehold electric appliances such as a personal computer and a portabletelephone, an electric vehicle, a railroad, a base station of a portabletelephone, a power plant and so forth.

A fuel cell includes a stack, multiple hydrogen pumps, a hydrogencirculation passage and a hydrogen supply passage.

The stack is obtained by sandwiching a solid polymer electrolytemembrane between a negative electrode and a positive electrode from bothsides so as to form a membrane electrode assembly, locating a pair ofseparators on both sides of the membrane electrode assembly so as tocompose a plate-like unit cell, and laminating and packaging a pluralityof such unit cells.

One end of the hydrogen supply passage is connected with the hydrogenpump via a regulator and an on-off valve, and the other end thereof isconnected with a part, which is close to the negative electrode of thestack, of the hydrogen circulation passage. Hydrogen flows from thehydrogen pump through the hydrogen supply passage, passes through thepart of the hydrogen circulation passage that is close to the negativeelectrode to be sent out to a portion on the negative electrode sidewithin the stack, and flows through a flow passage in the portion.Hydrogen, which has flown through the flow passage and is dischargedfrom the stack, flows through the hydrogen circulation passage and isreturned to the stack.

When hydrogen is supplied to the stack so that fuel gas containinghydrogen comes into contact with the negative electrode and oxidationgas containing oxygen such as air comes into contact with the positiveelectrode, an electrochemical reaction occurs on both of the electrodesand electromotive force is generated.

For the fuel cell, a hydrogen circulation system is employed where offgas (discharge gas containing unreacted hydrogen) discharged from thenegative electrode as described above is circulated to the portion onthe negative electrode side of the stack, which has enhanced the useefficiency of hydrogen. The unreacted hydrogen in the off gas isutilized for power generation of the fuel cell while impurities in theoff gas remain in the hydrogen circulation passage, causing a problem ofincreasing the concentration of impurities at the portion on thenegative electrode side as power generation is performed and therebylowering the power generation efficiency in the fuel cell. Accordingly,the off gas in the hydrogen circulation passage is purged to the outsideat appropriate timings.

Since the off gas also contains moisture that has transmitted throughthe electrolyte membrane from the positive electrode side, a gas-liquidseparator is located in the hydrogen circulation passage to separate gasfrom water, returning gas to the power generation unit while dischargingretained water at appropriate timings.

A solenoid valve is used as a discharge valve for gas or water. Since agas discharge valve, not only a water discharge valve, also has moisturecontained in gas as described above, a poppet part of such dischargevalve may be frozen depending on the outside temperature. This mayprevent the discharge valve from operating, making it impossible togenerate electricity. If the discharge valve is opened here, the poppetpart may be damaged and a hydrogen leak may occur in the case where thedischarge valve is for the hydrogen circulation passage.

Japanese Patent Application Laid-Open Publication No. H6-74361 disclosesthe invention of an anti-freeze circuit of a solenoid valve in whichcurrent having a polarity opposite to that of the drive current isapplied, in the state where no drive current flows through the drivewiring of the solenoid valve, to a drive wiring via a contact which ismade conductive when a relay circuit applying driving current to thesolenoid valve is not biased, to heat the drive wiring and preventfreezing.

SUMMARY

A typical solenoid valve, however, is opened even if current having apolarity opposite to that of the drive current is applied as in JapanesePatent Application Laid-Open Publication No. H6-74361. This has caused aproblem in that only a special solenoid valve may be used that would notbe opened by current with the opposite polarity.

The present disclosure has been made in view of the circumstancesdescribed above, and aims to provide: a fuel cell capable of favorablygenerating electricity while suppressing leakage of gas and preventingfreezing of a solenoid valve with a simple configuration; a controlmethod for a fuel cell; and a recording medium recording a computerprogram so as to allow a computer to read the program.

In a fuel cell according to the present disclosure comprising: a powergeneration unit configured to generate electricity by reacting hydrogenand oxygen; a solenoid valve for discharging gas or water emitted fromthe power generation unit to the outside; and a control unit configuredto control energization of the solenoid valve, a plurality of thesolenoid valves are aligned along a discharging direction in which thegas or the water is discharged, a temperature detection unit configuredto detect the temperature of a solenoid valve on the downstream side inthe discharging direction is provided, and if the temperature of thesolenoid valve is equal to or lower than a predetermined value, thecontrol unit energizes a solenoid valve on a more upstream side than thesolenoid valve on the downstream side, and closes at least one of theother solenoid valves aligned with the energized solenoid valve.

Here, “a plurality of the solenoid valves are aligned along adischarging direction in which the gas or the water is discharged” meansthat “multiple solenoid valves are aligned in a direction of discharginggas” and/or “multiple solenoid valves are aligned in a direction ofdischarging water,” and “in the case where gas and water aresimultaneously discharged, multiple solenoid valves are aligned in thedischarging direction for the gas and the water.”

In a fuel cell according to the present disclosure comprising: a powergeneration unit configured to generate electricity by reacting hydrogenand oxygen; a solenoid valve for discharging gas or water emitted fromthe power generation unit to the outside; and a control unit configuredto control energization of the solenoid valve, a plurality of thesolenoid valves are aligned along a direction in which the gas or thewater is discharged, a plurality of temperature detection unitsconfigured to detect temperatures of respective solenoid valves areprovided, and if the temperature of a solenoid valve on the downstreamside in the discharging direction is equal to or lower than the firstpredetermined value, the control unit energizes the solenoid valve whileclosing at least one of the other solenoid valves aligned with theenergized solenoid valve.

A control method according to the present disclosure for controlling afuel cell comprising a power generation unit configured to generateelectricity by reacting hydrogen and oxygen, a plurality of alignedsolenoid valves for discharging gas or water emitted from the powergeneration unit to the outside, a control unit configured to controlenergization of the solenoid valves, and a temperature detection unitconfigured to detect the temperature of a solenoid valve on thedownstream side in a discharging direction, comprises: detecting thetemperature of the solenoid valve, and if the temperature of thesolenoid valve is equal to or lower than a predetermined value,energizing a solenoid valve at a more upper stream side in the dischargedirection than the solenoid valve on the downstream side, and closing atleast one of the other solenoid valves aligned with the energizedsolenoid valve.

A control method according to the present disclosure for controlling afuel cell comprising a power generation unit configured to generateelectricity by reacting hydrogen and oxygen, a plurality of alignedsolenoid valves for discharging gas or water discharged from the powergeneration unit to the outside, a control unit configured to controlenergization of the solenoid valve, and a plurality of temperaturedetection units configured to detect the temperatures of respectivesolenoid valves, comprises: detecting the temperatures of the solenoidvalves respectively; and if the temperature of the solenoid valve on adownstream side in the discharging direction is equal to or lower than afirst predetermined value, energizing the solenoid valve while closingat least one of the other solenoid valves aligned with the energizedsolenoid valve.

A non-transitory computer readable recording medium according to thepresent disclosure records a computer program causing a computerconfigured to control a fuel cell comprising a power generation unitconfigured to generate electricity by reacting hydrogen and oxygen, aplurality of aligned solenoid valves for discharging gas or wateremitted from the power generation unit to the outside, a control unitconfigured to control energization of the solenoid valves, and atemperature detection unit configured to detect the temperature of asolenoid valve on a downstream side in the discharging direction, toexecute processing of obtaining a temperature of the solenoid valve,determining whether or not the temperature of the solenoid valve isequal to or lower than a predetermined value, and outputting, if it isdetermined that the temperature of the solenoid valve is equal to orlower than the predetermined value, a command to energize a solenoidvalve on a more upstream side in the discharging direction than thesolenoid valve on the downstream side, and to close at least one of theother solenoid valves aligned with the energized solenoid valve.

A non-transitory computer readable recording medium according to thepresent disclosure records a computer program causing a computerconfigured to control a fuel cell comprising: a power generation unitconfigured to generate electricity by reacting hydrogen and oxygen; aplurality of aligned solenoid valves for discharging gas or wateremitted from the power generation unit to the outside; a control unitconfigured to control energization of the solenoid valves; and aplurality of temperature detection units configured to detecttemperatures of solenoid valves respectively, to execute processing ofobtaining temperatures of the solenoid valves respectively, determiningwhether or not the temperature of a solenoid valve on the downstreamside in the discharging direction is equal to or lower than a firstpredetermined value, and outputting, if it is determined that thetemperature of the solenoid valve is equal to or lower than the firstpredetermined value, a command to energize the solenoid valve and toclose at least one of the other solenoid valves aligned with theenergized solenoid valve.

According to the present disclosure, a simple configuration may suppressleakage of gas, prevent freezing of solenoid valves and thus achievefavorable power generation.

The above and further objects and features will more fully be apparentfrom the following detailed description with accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a fuel cell according toEmbodiment 1;

FIG. 2 is a flowchart illustrating second energization processingperformed by a CPU;

FIG. 3 is a block diagram illustrating a fuel cell according toEmbodiment 2;

FIG. 4 is a flowchart illustrating second energization processingperformed by a CPU;

FIG. 5 is a block diagram illustrating a fuel cell according toEmbodiment 3;

FIG. 6 is a flowchart illustrating second energization processingperformed by a CPU;

FIG. 7 is a block diagram illustrating a fuel cell according toEmbodiment 4; and

FIG. 8 is a flowchart illustrating second energization processingperformed by a CPU.

DETAILED DESCRIPTION

The present disclosure will specifically be described below withreference to the drawings illustrating the embodiments thereof.

Embodiment 1

FIG. 1 is a block diagram illustrating a fuel cell 300 according toEmbodiment 1.

The fuel cell 300 is provided with a cell body 100 and a hydrogen supplyunit 200. The cell body 100 is a cell body such as a solid polymerelectrolyte fuel cell, for example.

The cell body 100 is provided with a stack 1, a hydrogen flow passage 2(hydrogen supply passage 2 a and hydrogen circulation passage 2 b), anair flow passage 3, a stack cooling passage 4, a radiator flow passage5, a cylinder heating passage 6, a first heat exchanger 7, a second heatexchanger 8, a control unit 9, a gas-liquid separator 27, drain valves28 and 29, a hydrogen circulation pump 26, an air pump 30, a coolingpump 40, a heat radiation pump 50, a radiator 51, a fan 52, a heatingpump 60, exhaust valves 61 and 62, a temperature sensor 63, a drainage75 and an exhaust passage 76. The second heat exchanger 8 is providedwith a heater (not illustrated).

The hydrogen supply unit 200 is provided with a plurality of metalhydride (MH) cylinders 20, an on-off valve 21 and a regulator 22. EachMH cylinder 20 is filled with a hydrogen storage alloy. The on-off valve21 is connected with all of the MH cylinders 20 and is also connectedwith the regulator 22. The supply pressure of hydrogen is adjusted bythe regulator 22. A reaction occurred when the hydrogen storage alloy inthe MH cylinders 20 releases hydrogen is an endothermic reaction.

The stack 1 is obtained by sandwiching a solid polymer electrolytemembrane between a negative electrode and a positive electrode from bothsides so as to form a membrane electrode assembly, locating a pair ofseparators on both sides of the membrane electrode assembly so as tocompose a plate-like unit cell, and laminating and packaging a pluralityof such unit cells.

When fuel gas containing hydrogen, which has flown in from the hydrogensupply unit 200, comes into contact with the negative electrode andoxidation gas containing oxygen such as air flows in from the air flowpassage 3 and comes into contact with the positive electrode, anelectrochemical reaction occurs on both electrodes and electromotiveforce is generated. In this electrochemical reaction, water is generatedfrom a reaction between a hydrogen ion, which has been transmittedthrough the solid polymer electrolyte membrane from the negativeelectrode side, and oxygen in the oxidation gas.

One end of the hydrogen supply passage 2 a is connected with theregulator 22, while the other end thereof is connected with a part,which is close to the negative electrode of the stack 1, of the hydrogencirculation passage 2 b. The hydrogen supply passage 2 a is providedwith an on-off valve 23, an on-off valve 24 and a check valve 25, whichare positioned in this order from the hydrogen supply unit 200 side.

The hydrogen circulation pump 26 is provided at the hydrogen circulationpassage 2 b. The fuel cell 300 is constructed in such a manner that,when the on-off valve 23 and the on-off valve 24 are opened, hydrogenflows from the regulator 22 through the hydrogen supply passage 2 a viathe on-off valve 23, the on-off valve 24 and the check valve 25, ispumped by the hydrogen circulation pump 26 to flow through the hydrogencirculation passage 2 b, and is sent out to a part on the negativeelectrode side of the stack 1 to flow through a flow passage in thispart. Hydrogen, impurities (including impurities originally contained inhydrogen as well as impurities generated by reaction) and moisture,which have flown through the flow passage and are discharged from thestack 1, flow through the hydrogen circulation passage 2 b and are sentto the gas-liquid separator 27.

In the gas-liquid separator 27, the hydrogen and the like are separatedinto water and gas containing hydrogen and impurities.

The drainage 75 is connected with the lower side of the gas-liquidseparator 27, and is provided with the drain valves 28 and 29, which areelectromagnetic valves, arranged in series.

The exhaust passage 76 is branched at the upper side of the gas-liquidseparator 27 to extend from the hydrogen circulation passage 2 b, and isprovided with exhaust valves 61 and 62 arranged in series fordischarging the gas. The gas flows through the exhaust passage 76 byenergizing and opening the exhaust valves 61 and 62 at an appropriatetiming, and is discharged to the outside.

At the gas-liquid separator 27, when the discharge valves 61 and 62 areclosed, the separated gas flows from the gas-liquid separator 27 throughthe hydrogen circulation passage 2 b to be sent to the hydrogencirculation pump 26 and to be returned to the stack 1. The waterobtained by separation at the gas-liquid separator 27 is stored and, ifit reaches a predetermined amount, the discharge valves 28 and 29 areenergized and opened so that the water flows through the drainage 75 andis discharged to the outside.

The discharge valves 28 and 29 are covered with heat insulatingmaterials 81 and 82, respectively. A portion of the drainage 75 betweenthe discharge valves 28 and 29 is also covered with a heat insulatingmaterial. The portion covered with the heat insulating material isindicated by a thick line in FIG. 1. Though not required, a heatinsulating material may preferably be employed as it may retain the heatgenerated by energization of the discharge valve 28 or 29 in the case ofperforming the second energization processing, which will be describedlater, and thus may more favorably prevent freezing. It is also possibleto cover the entire drainage 75 with a heat insulating material.

The discharge valves 61 and 62 are covered with heat insulatingmaterials 83 and 84, respectively. A portion of the drainage 76 betweenthe discharge valves 61 and 62 is also covered with a heat insulatingmaterial. The portion covered with the heat insulating material isindicated by a thick line in FIG. 1. Though not required, a heatinsulating material may preferably be employed as it may retain the heatgenerated by energization of the discharge valve 61 or 62 in the case ofperforming the second energization processing, which will be describedlater, and thus may more favorably prevent freezing. It is also possibleto cover the entire drainage 76 with a heat insulating material.

The air pump 30 is provided at the air flow passage 3. In addition, anon-off valve 31 is provided at an inlet side part of the air flowpassage 3 to the stack 1, and an on-off valve 32 is provided at anoutlet side part thereof from the stack 1. The fuel cell 300 isconstructed in such a manner that, when the on-off valve 31 and theon-off valve 32 are opened, air sent out from the air pump 30 flowsthrough the air flow passage 3 and the on-off valve 31, is guided into apositive electrode side part of the stack 1, and flows through a flowpassage of this part. Air, which has flown through the flow passage, isdischarged from the stack 1, and is discharged through the on-off valve32 to the outside.

A cooling pump 40, an ion exchange resin 43 and a conductivity meter 44are provided at the stack cooling passage 4. The fuel cell 300 isconstructed in a such manner that cooling water, which is sent out fromthe cooling pump 40 and flows through the stack cooling passage 4, flowsthrough the ion exchange resin 43, the conductivity of the cooling wateris measured by the conductivity meter 44, and the cooling water is thenguided into the stack 1, flows through a flow passage in the stack 1, isthen discharged, flows through the first heat exchanger 7 and the secondheat exchanger 8, and returns to the cooling pump 40. The ion exchangeresin 43 adsorbs ions included in cooling water which flows through thestack cooling passage 4. When the ion content becomes high, theconductivity of cooling water becomes high and the power generationefficiency of the stack 1 is lowered. It is therefore necessary to causethe ion exchange resin 43 to adsorb metal ions or the like.

The heat radiation pump 50 is provided at the radiator flow passage 5.The fuel cell 300 is constructed in a such manner that heat radiationliquid such as antifreeze liquid sent out from the heat radiation pump50 flows through the radiator 51, further flows through the first heatexchanger 7, and then returns to the heat radiation pump 50.

The fan 52 is provided in proximity to the radiator 51.

The heating pump 60 is provided at the cylinder heating passage 6. Thefuel cell 300 is constructed in such a manner that heating liquid sentout from the heating pump 60 flows through a flow passage in thehydrogen supply unit 200 while heating each MH cylinder 20, is thendischarged from the hydrogen supply unit 200, flows through the secondheat exchanger 8, and returns to the heating pump 60. Hydrogen isreleased from the hydrogen storage alloy in each MH cylinder 20 byheating. An example of heating liquid is antifreeze liquid.

The stack cooling passage 4, the radiator flow passage 5, the cylinderheating passage 6, the first heat exchanger 7 and the second heatexchanger 8 are covered with heat insulating material. The portionscovered with the heat insulating material are indicated by thick linesin FIG. 1. The heat insulating material makes it possible to restrictheat transfer to/from the outside and to easily control the heatquantity.

The control unit 9 is provided with a CPU (Central Processing Unit) 90configured to control operations of the respective components of thecontrol unit 9, and the CPU 90 is connected with a ROM 91 and a RAM 92via a bus.

The ROM 91 is a nonvolatile memory such as an electrically erasableprogrammable read-only memory (EEPROM), which stores an operatingprogram 91 a for the fuel cell 300 as well as an antifreeze program 91 baccording to the present embodiment.

Moreover, the antifreeze program 91 b may be recorded on a recordingmedium such as a CD (Compact Disc)-ROM, which is a portable medium forcomputer-readable recording, a DVD (Digital Versatile Disc)-ROM, a BD(Blu-ray (registered trademark) Disc), a hard disc drive or asolid-state drive, so that the CPU 90 reads out the antifreeze program91 b from the recording medium and stores the antifreeze program 91 b inthe ROM 91.

Furthermore, the antifreeze program 91 b according to the presentdisclosure may also be acquired from an external computer (notillustrated) that is connected to a communication network, and be storedin the ROM 91.

The RAM 92 is a memory such as a DRAM (Dynamic RAM) or an SRAM (StaticRAM), and temporarily stores the operating program 91 a as well as theantifreeze program 91 b that are read out from the ROM 91 in the processof executing arithmetic processing by the CPU 90, and various data thatare generated in the arithmetic processing executed by the CPU 90.

The control unit 9 is connected with the respective components of thecell body 100 and with the on-off valve 21 of the hydrogen supply unit200, to control the operations of the respective components and theon-off valve 21. As for the connection between the control unit 9 andthe components, only the portions necessary for the description of thepresent embodiment are illustrated.

A reaction occurring at the stack 1 is an exothermic reaction, and thestack 1 is cooled by cooling water, which flows through the stackcooling passage 4. Heat of cooling water, which has been discharged fromthe stack 1, is conducted to heat radiation liquid at the first heatexchanger 7, the heat radiation liquid radiates heat at the radiator 51,and the heat is radiated to the outside of the cell body 100 by the fan52. Heat radiation liquid, which has been cooled at the radiator 51, issent to the first heat exchanger 7.

Heat of cooling water, which has flown through the first heat exchanger7 and has been guided into the second heat exchanger 8 in the stackcooling passage 4, is conducted to heating liquid at the second heatexchanger 8, and the heating liquid heats each MH cylinder 20 of thehydrogen supply unit 200, and releases hydrogen from the hydrogenstorage alloy.

Cooling water, which has been cooled at the second heat exchanger 8,returns to the cooling pump 40 and is sent to the stack 1.

While the temperature of cooling water in the stack cooing passage 4depends on the environmental temperature when power is not beinggenerated, it is possible to maintain each MH cylinder 20 at apredetermined temperature by heating the heating liquid with the heaterof the second heat exchanger 8.

It is also possible to send air, which includes heat generated at thestack 1, to the hydrogen supply unit 200 so as to heat each MH cylinder20, without providing the cylinder heating passage 6. Furthermore, aheater may be provided in each MH cylinder 20 so as to directly heat theMH cylinder 20.

The cell body 100 is provided with the temperature sensor 63, whichdetects environmental temperature.

According to the present embodiment, the CPU 90 controls energization ofthe drain valves 28, 29 and the exhaust valves 61, 62 based on theenvironmental temperature detected by the temperature sensor 63.

The CPU 90 of the control unit 9 reads out the antifreeze program 91 bfrom the ROM 91, and executes energization processing for freezeproofing.

Energization processing for freeze proofing will now be described below.Hereinafter, the energization processing will be referred to as thesecond energization processing in order to distinguish it from theenergization processing performed in the case of discharging gas orwater.

FIG. 2 is a flowchart illustrating second energization processingperformed by the CPU 90.

Initially, all of the exhaust valves 61, 62 and drain valves 28, 29 arein the state of energization off.

First, the CPU 90 determines whether or not the environmentaltemperature Te obtained from the temperature sensor 63 is 5° C. orhigher (S1).

If it is determined that the environmental temperature Te is 5° C. orhigher (S1: YES), the CPU 90 turns off the energization of the exhaustvalve 61 (S2), turns off the energization of the exhaust valve 62 (S3),turns off the energization of the drain valve 28 (S4), turns off theenergization of the drain valve 29 (S5), and proceeds to step S17.

If it is determined that the environmental temperature Te is not 5° C.or higher (S1: NO), the CPU 90 determines whether or not theenergization of the exhaust valve 61 is in the off state (S6).

If it is determined that the energization of the exhaust valve 61 is inthe off state (S6: YES), the CPU 90 turns off the energization of theexhaust valve 62 (S7), turns on the energization of the exhaust valve 61(S8), and proceeds to step S11. Here, though the amount of current inthe energization of the exhaust valve 61 may be an amount enough tofully open the exhaust valve 61, such an amount of current that is ableto heat the exhaust valve 61 to at least prevent the exhaust valve 61from being frozen may be sufficient. Moreover, the amount of current maybe changed depending on the outside temperature. For example, if theoutside temperature is not too low, such as −1° C. or −2° C., the amountof current may be small. The relationships between the outsidetemperature, amount of current and duration of energization, which willbe described later, may be decided based on experimentation, and a tableshowing such relationships may be stored in the ROM 91. The duration ofenergization (hereinafter also referred to as energization time) may bechanged in accordance with the outside temperature.

If it is determined that the energization of the exhaust valve 61 is notin the off state (S6: NO), the CPU 90 turns off the energization of theexhaust valve 61 (S9), turns on the energization of the exhaust valve 62(S10), and proceeds to step S11. The amount of electricity distributedto the exhaust valve 62 is decided similarly to that for the exhaustvalve 61. Moreover, the exhaust valve 62 may have a larger amount ofcurrent or a longer energization time compared to the exhaust valve 61,since it is located more toward the downstream side than the exhaustvalve 61 and thus tends to be cooler.

The CPU 90 determines, at step S11, whether or not the energization ofthe exhaust valve 28 is in the off state.

If it is determined that the energization of the exhaust valve 28 is inthe off state (S11: YES), the CPU 90 turns off the energization of thedrain valve 29 (S12), turns on the energization of the drain valve 28(S13), and proceeds to step S16. The amount of electricity distributedto the drain valve 28 is also decided similarly to that for the exhaustvalve 61 or the like.

If it is determined that the energization of the drain valve 28 is notin the off state (S11: NO), the CPU 90 turns off the energization of thedrain valve 28 (S14), turns on the energization of the drain valve 29(S15), and proceeds to step S16. The amount of electricity distributedto the drain valve 29 is also decided similarly to that for the exhaustvalve 61 or the like.

At step S16, the CPU 90 determines whether or not a predefinedenergization time has elapsed for a solenoid valve that is currentlyopen. The energization time is defined in advance based onexperimentation or the like, and is stored in the ROM 91. It is alsopossible to determine the elapse of the energization time individuallyfor each of open solenoid valves.

If it is determined that the energization time has not elapsed (S16:NO), the CPU 90 repeats the determination processing.

If it is determined that the energization time has elapsed (S16: YES),the CPU 90 determines whether or not the second energization processingis terminated (S17). The determination on termination of the secondenergization processing is made based on, for example, whether or notthe state where the environmental temperature Te is 5° C. or highercontinues for a predetermine period of time, whether or not the totaltime of the second energization processing for the open solenoid valvesexceeds a predetermined period of time, whether or not the number oftimes the second energization processing is performed for the opensolenoid valves exceeds a predetermined number, and whether or not aninstruction from the user to terminate the second energizationprocessing is accepted.

If it is determined that the second energization processing is notterminated (S17: NO), the CPU 90 returns the processing to step S1.

If it is determined that the second energization processing isterminated (S17: YES), the CPU 90 turns off the energization of thedrain valve 28 and the exhaust valve 61 (S18), then turns off theenergization of the drain valve 29 and the exhaust valve 62 (S19), andterminates the second energization processing. In the case ofterminating the second energization processing, the solenoid valves areclosed in sequence from the upstream side in the discharging direction,leaving no pressure between the solenoid valves and thus effectivelypreventing any hydrogen leakage. Moreover, moisture is unlikely toremain, which favorably prevents freezing.

According to the present embodiment, in the case where the environmentaltemperature Te is 5° C. or higher which is not a freezing condition, itis not necessary to heat any of the exhaust valves 61, 62 and drainvalves 28, 29, and therefore all the valves are maintained to be in thestate of energization off.

In the case where the environmental temperature Te is lower than 5° C.,first, the exhaust valve 61 is energized to be heated while the exhaustvalve 62 is in the energization off state, and the drain valve 28 isenergized to be heated while the drain valve 29 is in the energizationoff state. In the case where the environmental temperature Te continuesto be lower than 5° C., the energization of the exhaust valve 61 isturned off and the exhaust valve 62 is energized to be heated, while theenergization of the drain valve 28 is turned off and the drain valve 29is energized to be heated.

Since the solenoid valves are switched when the energization time haselapsed, i.e., the energization of the solenoid valves aligned in seriesare alternately turned on, each of the solenoid valves has the dutyratio of 1:1.

In the present embodiment, as the environmental temperature Te isdetected while the actual temperature of each solenoid valve is unknown,the solenoid valves aligned in series are alternately turned on to beenergized so as to favorably prevent the solenoid valves from beingfrozen. Thus, power generation may favorably be performed.

While the solenoid valve on the upstream side in the gas or waterdischarging direction is energized first in the present embodiment, theorder of energization is not limited thereto, but the solenoid valve onthe downstream side may also be energized first.

Embodiment 2

FIG. 3 is a block diagram illustrating a fuel cell 301 according toEmbodiment 2. In FIG. 3, parts corresponding to those in FIG. 1 will bedenoted by the same reference numerals and will not be described indetail.

The exhaust valve 62 and the drain valve 29 of the fuel cell 301 may beprovided with temperature sensors 64 and 65, respectively.

FIG. 4 is a flowchart illustrating second energization processingperformed by the CPU 90.

Initially, all of the exhaust valves 61, 62 and the drain valves 28, 29are in the state of energization off.

First, the CPU 90 determines whether or not the temperature Ta of theexhaust valve 62 obtained from the temperature sensor 64 is 5° C. orhigher (S21).

If it is determined that the temperature Ta is 5° C. or higher (S21:YES), the CPU 90 turns off the energization of the exhaust valve 61(S22), turns off the energization of the exhaust valve 62 (S23), andproceeds to step S29.

If it is determined that the temperature Ta is not 5° C. or higher (S21:NO), the CPU 90 determines whether or not the energization of theexhaust valve 61 is in the off state (S24).

If it is determined that the energization of the exhaust valve 61 is inthe off state (S24: YES), the CPU 90 turns off the energization of theexhaust valve 62 (S25), turns on the energization of the exhaust valve61 (S26), and proceeds to step S29. Here, though the amount of currentin the energization of the exhaust valve 61 may be an amount enough tofully open the exhaust valve 61, such an amount of current that is ableto heat the exhaust valve 61 to at least prevent the exhaust valve 61from being frozen may be sufficient. Moreover, the amount of current maybe changed depending on the temperature of the exhaust valve 62. Forexample, if the temperature of the exhaust valve 62 is not too low, suchas −1° C. or −2° C., the amount of current may be small. Therelationships between the temperature of the exhaust valve 62, an amountof current supplied to the exhaust valve 61 and energization time may bedecided based on experimentation, and a table showing such relationshipsmay be stored in the ROM 91.

If it is determined that the energization of the exhaust valve 61 is notin the off state (S24: NO), the CPU 90 turns off the energization of theexhaust valve 61 (S27), turns on the energization of the exhaust valve62 (S28), and proceeds to step S29. The amount of electricitydistributed to the exhaust valve 62 is decided similarly to that for theexhaust valve 61.

The CPU 90 determines, at step S29, whether or not the temperature Tb ofthe drain valve 29 obtained from the temperature sensor 65 is 5° C. orhigher.

If it is determined that the temperature Tb is 5° C. or higher (S29:YES), the CPU 90 turns off the energization of the drain valve 28 (S30),turns off the energization of the drain valve 29 (S31), and proceeds tostep S37.

If it is determined that the temperature Tb is not 5° C. or higher (S29:NO), the CPU 90 determines whether or not the energization of the drainvalve 28 is in the off state (S32).

If it is determined that the energization of the drain valve 28 is inthe off state (S32: YES), the CPU 90 turns off the energization of thedrain valve 29 (S33), turns on the energization of the drain valve 28(S34), and proceeds to step S37. The amount of electricity distributedto the drain valve 28 is also decided similarly to that for the exhaustvalve 61.

If it is determined that the energization of the drain valve 28 is notin the off state (S32: NO), the CPU 90 turns off the energization of thedrain valve 28 (S35), turns on the energization of the drain valve 29(S36), and proceeds to step S37. The amount of electricity distributedto the drain valve 29 is also decided similarly to the exhaust valve 61or the like.

The CPU 90 determines, at step S37, whether or not all of the exhaustvalves 61, 62 and the drain valves 28, 29 are in the off state. If it isdetermined that all of the valves are in the off state (S37: YES), theCPU 90 returns the processing to step S21.

If it is determined that not all of the valves are in the off state(S37: NO), the CPU 90 determines whether or not a prescribedenergization time has elapsed for a solenoid valve that is currentlyopen (S38). It is also possible to determine the elapse of theenergization time individually for each of open solenoid valves. If itis determined that the energization time has not elapsed (S38: NO), theCPU 90 repeats the determination processing.

If it is determined that the energization time has elapsed (S38: YES),the CPU 90 determines whether or not the second energization processingis terminated (S39). The determination on termination of the secondenergization processing is made based on, for example, whether or notthe state where the temperature Ta and Tb are 5° C. or higher continuesfor a predetermine period of time, whether or not the total time of thesecond energization processing for open solenoid valves exceeds apredetermined period of time, whether or not the number of times thesecond energization processing is performed for the open solenoid valvesexceeds a predetermined number, and whether or not an instruction fromthe user to terminate the second energization processing is accepted.

If it is determined that the second energization processing is notterminated (S39: NO), the CPU 90 returns the processing to step S21.

If it is determined that the second energization processing isterminated (S39: YES), the CPU 90 turns off the energization of thedrain valve 28 and the exhaust valve 61 (S40), then turns off theenergization of the drain valve 29 and the exhaust valve 62 (S41), andterminates the second energization processing.

According to the present embodiment, in the case where the temperatureTa and Tb are 5° C. or higher which is not a freezing condition, it isnot necessary to heat any of the exhaust valves 61, 62 and drain valves28, 29, and therefore all the valves are maintained to be in the stateof energization off.

In the case where the temperature Ta of the exhaust valve 62 is lowerthan 5° C., first, the exhaust valve 61 is energized to be heated whilethe exhaust valve 62 is in the energization off state. In the case wherethe temperature Ta continues to be lower than 5° C., then theenergization of the drain valve 61 is turned off and the drain valve 62is energized to be heated. Likewise, in the case where the temperatureTb of the drain valve 29 is lower than 5° C., first, the drain valve 28is energized to be heated while the drain valve 29 is in theenergization off state. In the case where the temperature Tb continuesto be lower than 5° C., the energization of the drain valve 28 is turnedoff to energize and heat the drain valve 29.

In the present embodiment, the temperature sensor is provided only atthe solenoid valve on the downstream side in the gas and waterdischarging direction, so that the solenoid valve on the upstream sidewhere no temperature sensor is provided is energized first and heated.If the solenoid valve where the temperature sensor is provided is heatedfirst, the temperature of the solenoid valve where no temperature sensoris provided may be lowered, which may freeze the solenoid valve. If thesolenoid valve on the upstream side is heated, the heated gas or waterflows through the solenoid valve on the downstream side while heatingthe solenoid valve on the downstream side.

As the energization time elapses, the energization of the solenoidvalves aligned in series are alternately turned on, so that each valvehas the duty ratio of 1:1.

Embodiment 3

FIG. 5 is a block diagram illustrating a fuel cell 302 according toEmbodiment 3. In FIG. 5, parts corresponding to those in FIG. 3 will bedenoted by the same reference numerals and will not be described indetail.

As in the fuel cell 301, the exhaust valve 62 and the drain valve 29 areprovided with temperature sensors 64 and 65, respectively, while theexhaust valve 61 and the drain valve 28 are provided with thetemperature sensors 66 and 67, respectively.

FIG. 6 is a flowchart illustrating second energization processingperformed by the CPU 90.

Initially, all of the exhaust valves 61, 62 and drain valves 28, 29 arein the state of energization off.

First, the CPU 90 determines whether or not the temperature Ta of theexhaust valve 62 obtained from the temperature sensor 64 is 5° C. orhigher (S51).

If it is determined that the temperature Ta is 5° C. or higher (S51:YES), the CPU 90 turns off the energization of the exhaust valve 61(S52), turns off the energization of the exhaust valve 62 (S53), andproceeds to step S60.

If it is determined that the temperature Ta is not 5° C. or higher (S51:NO), the CPU 90 determines whether or not the energization of theexhaust valve 62 is in the off state (S54).

If it is determined that the energization of the exhaust valve 62 is inthe off state (S54: YES), the CPU 90 turns off the energization of theexhaust valve 61 (S55), turns on the energization of the exhaust valve62 (S26), and proceeds to step S60. Here, though the amount of currentin the energization of the exhaust valve 62 may be an amount enough tofully open the exhaust valve 62, such an amount of current that is ableto heat the exhaust valve 62 to at least prevent the exhaust valve 62from being frozen may be sufficient. Moreover, the amount of current maybe changed depending on the temperature of the exhaust valve 62. Forexample, if the temperature of the exhaust valve 62 is not too low, suchas −1° C. or −2° C., the amount of current may be small. Therelationships between the temperature of the exhaust valve 62, theamount of current supplied to the exhaust valve 62 and the energizationtime may be decided based on experimentation, and a table showing suchrelationships may be stored in the ROM 91.

If it is determined that the energization of the exhaust valve 62 is notin the off state (S54: NO), the CPU 90 determines whether or not thetemperature Tc of the exhaust valve 61 obtained from the temperaturesensor 66 is 5° C. or higher (S57).

If it is determined that the temperature Tc is 5° C. or higher (S57:YES), the CPU 90 proceeds to step S55.

If it is determined that the temperature Tc is not 5° C. or higher (S57:NO), the CPU 90 turns off the energization of the exhaust valve 62(S58), turns on the energization of the exhaust valve 61 (S59), andproceeds to step S60. The amount of electricity distributed to theexhaust valve 61 is also decided similarly to the amount of electricitydistributed to the exhaust valve 62.

The CPU 90 determines, at step S60, whether or not the temperature Tb ofthe drain valve 29 obtained from the temperature sensor 65 is 5° C. orhigher.

If it is determined that the temperature Tb is 5° C. or higher (S60:YES), the CPU 90 turns off the energization of the drain valve 28 (S61),turns off the energization of the drain valve 29 (S62), and proceeds tostep S69.

If it is determined that the temperature Tb is not 5° C. or higher (S60:NO), the CPU 90 determines whether or not the energization of the drainvalve 29 is in the off state (S63).

If it is determined that the energization of the drain valve 29 is inthe off state (S63: YES), the CPU 90 turns off the energization of thedrain valve 28 (S64), turns on the energization of the drain valve 29(S65), and proceeds to step S69. The amount of electricity distributedto the drain valve 29 is also decided similarly to the amount ofelectricity distributed to the exhaust valve 62 or the like.

If it is determined that the energization of the drain valve 29 is notin the off state (S63: NO), the CPU 90 determines whether or not thetemperature Td of the drain valve 28 obtained from the temperaturesensor 67 is 5° C. or higher (S66).

If it is determined that the temperature Td is 5° C. or higher (S66:YES), the CPU 90 proceeds to step S64.

If it is determined that the temperature Td is not 5° C. or higher (S66:NO), the CPU 90 turns off the energization of the drain valve 29 (S67),turns on the energization of the drain valve 28 (S68), and proceeds tostep S69. The amount of electricity distributed to the drain valve 28 isalso decided similarly to the amount of electricity distributed to thedrain valve 29.

The CPU 90 determines, at step S69, whether or not all of the exhaustvalves 61, 62 and the drain valves 28, 29 are in the off state. If it isdetermined that all of the valves are in the off state (S69: YES), theCPU 90 returns the processing to step S51.

If it is determined that not all of the valves are in the off state(S69: NO), the CPU 90 determines whether or not a prescribedenergization time has elapsed for a solenoid valve that is currentlyopen (S70). It is also possible to determine the elapse of theenergization time individually for each of the open solenoid valves.

If it is determined that the energization time has not elapsed (S70:NO), the CPU 90 repeats the determination processing.

If it is determined that the energization time has elapsed (S70: YES),the CPU 90 determines whether or not the second energization processingis terminated (S71). The determination on termination of the secondenergization processing is made based on, for example, whether or notthe state where the temperatures Ta, Tb, Tc and Td are 5° C. or highercontinues for a predetermine period of time, whether or not the totaltime of the second energization processing for the open solenoid valvesexceeds a predetermined period of time, whether or not the number oftimes the second energization processing is performed for the opensolenoid valves exceeds a predetermined number, and whether or not aninstruction from the user to terminate the second energizationprocessing is accepted.

If it is determined that the second energization processing is notterminated (S71: NO), the CPU 90 returns the processing to step S51.

If it is determined that the second energization processing isterminated (S71: YES), the CPU 90 turns off the energization of thedrain valve 28 and the exhaust valve 61 (S72), then turns off theenergization of the drain valve 29 and the exhaust valve 62 (S73), andterminates the second energization processing.

According to the present embodiment, in the case where the temperaturesTa and Tb are 5° C. or higher, all the solenoid valves are maintained tobe in the state of energization off.

In the case where the temperature Ta of the exhaust valve 62 is lowerthan 5° C., first, the exhaust valve 62 is energized to be heated whilethe exhaust valve 61 is in the state of energization off. In the casewhere the temperature Ta continues to be lower than 5° C., theenergization of the exhaust valve 62 is maintained when the temperatureTc of the exhaust valve 61 is 5° C. or higher. Thus, the exhaust valve62 may remain energized until it is warmed up. In the case where thetemperature Tc of the exhaust valve 61 is lower than 5° C., theenergization of the exhaust valve 62 is turned off and the exhaust valve61 is energized to be heated. In this case also, the gas that has flownthrough the exhaust valve 61 warms up the exhaust valve 62.

Likewise, in the case where the temperature Tb of the drain valve 29 islower than 5° C., first, the drain valve 29 is energized to be heatedwhile the drain valve 28 is in the state of energization off. In thecase where the temperature Tb continues to be lower than 5° C., theenergization of the drain valve 29 is maintained when the temperature Tdof the drain valve 28 is 5° C. or higher. In the case where thetemperature Td of the drain valve 28 is lower than 5° C., theenergization of the drain valve 29 is turned off and the drain valve 28is energized to be heated.

In the present embodiment, the temperature sensor is provided at both ofthe solenoid valves on the upstream side and downstream side in the gasand water discharging direction, so that the solenoid valve on thedownstream side that is likely to be frozen is energized first andheated.

The solenoid valves aligned in series are not alternately energized,resulting in increased energization time of the solenoid valve on thedownstream side that is likely to be frozen, each solenoid valve nothaving the duty ratio of 1:1.

According to the present embodiment, the temperature of each solenoidvalve is detected to energize a solenoid valve as needed, therebypreventing supply of unnecessary electricity.

Embodiment 4

FIG. 7 is a block diagram illustrating a fuel cell 303 according toEmbodiment 4. In FIG. 7, parts corresponding to those in FIG. 5 will bedenoted by the same reference numerals and will not be described indetail.

In the fuel cell 303, an exhaust drain passage 77 is connected with agas-liquid separator 27 at the lower side, and is provided with anexhaust drain valve 68 and an exhaust drain valve 69 arranged in series.The exhaust drain valves 68 and 69 are provided with temperature sensors73 and 74, respectively. The exhaust drain valves 68 and 69 are coveredwith heat insulating materials 85 and 86, respectively. A portion of theexhaust drain passage 77 between the exhaust drain valves 68 and 69 isalso covered with a heat insulating material. The portions covered withthe heat insulating material are indicated by thick lines in FIG. 7.Though not required, a heat insulating material may preferably beemployed as it may retain the heat generated by energization of theexhaust drain valve 68 or 69 in the case of performing the secondenergization processing, and thus may more favorably prevent freezing.It is also possible to cover the entire exhaust drain passage 77 with aheat insulating material. According to the present embodiment, water isstored in the gas-liquid separator 27 and if the amount of stored waterreaches a predetermined value or higher, or if an amount of impuritiesin the gas is increased, the exhaust drain valve 68 and the exhaustdrain valve 69 are simultaneously opened so as to discharge water andgas at the same time.

FIG. 8 is a flowchart illustrating second energization processingperformed by the CPU 90.

Initially, the exhaust drain valve 68 and the exhaust drain valve 69 areboth in the state of energization off.

First, the CPU 90 determines whether or not the temperature Tf of theexhaust drain valve 69 obtained from the temperature sensor 74 is 5° C.or higher (S81).

If it is determined that the temperature Tf is 5° C. or higher (S81:YES), the CPU 90 turns off the energization of the exhaust drain valve68 (S82), turns off the energization of the exhaust drain valve 69(S83), and proceeds to step S90.

If it is determined that the temperature Tf is not 5° C. or higher (S81:NO), the CPU 90 determines whether or not the energization of theexhaust drain valve 69 is in the off state (S84).

If it is determined that the energization of the exhaust drain valve 69is in the off state (S84: YES), the CPU 90 turns off the energization ofthe exhaust drain valve 68 (S85), turns on the energization of theexhaust drain valve 69 (S86), and proceeds to step S90. Here, though theamount of current in the energization of the exhaust drain valve 69 maybe an amount enough to fully open the exhaust drain valve 69, such anamount of current that is able to heat the exhaust drain valve 69 to atleast prevent the exhaust drain valve 69 from being frozen may besufficient. Moreover, the amount of current may be changed depending onthe temperature of the exhaust drain valve 69. For example, if thetemperature of the exhaust drain valve 69 is not too low, such as −1° C.or −2° C., the amount of current may be small. The relationships betweenthe temperature of the exhaust drain valve 69, the amount of currentsupplied to the exhaust drain valve 69 and the energization time may bedecided based on experimentation, and a table showing such relationshipsmay be stored in the ROM 91.

If it is determined that the energization of the exhaust drain valve 69is not in the off state (S84: NO), the CPU 90 determines whether or notthe temperature Tg of the exhaust drain valve 68 obtained from thetemperature sensor 73 is 5° C. or higher (S87).

If it is determined that the temperature Tg is 5° C. or higher (S87:YES), the CPU 90 proceeds to step S85.

If it is determined that the temperature Tg is not 5° C. or higher (S87:NO), the CPU 90 turns off the energization of the exhaust drain valve 69(S88), turns on the energization of the exhaust drain valve 68 (S89),and proceeds to step S90. The amount of electricity distributed to theexhaust drain valve 68 is also decided similarly to the amount ofelectricity distributed to the exhaust drain valve 68.

The CPU 90 determines, at step S90, whether or not both of the exhaustdrain valves 68 and 69 are in the off state. If it is determined thatboth of the exhaust drain valves 68 and 69 are in the off state (S90:YES), the CPU 90 returns the processing to step S81.

If it is determined that not both of the exhaust drain valves 68 and 69are in the off state (S90: NO), the CPU 90 determines whether or not aprescribed energization time has elapsed for a solenoid valve that iscurrently open (S91). If it is determined that the energization time hasnot elapsed (S91: NO), the CPU 90 repeats the determination processing.

If it is determined that the energization time has elapsed (S91: YES),the CPU 90 determines whether or not the second energization processingis terminated (S92). The determination on termination of the secondenergization processing is made based on, for example, whether or notthe state where the temperatures Tf and Tg are 5° C. or higher continuesfor a predetermine period of time, whether or not the total time of thesecond energization processing for an open solenoid valve exceeds apredetermined period of time, whether or not the number of times thesecond energization processing is performed for an open solenoid valveexceeds a predetermined number, and whether or not an instruction fromthe user to terminate the second energization processing is accepted.

If it is determined that the second energization processing is notterminated (S92: NO), the CPU 90 returns the processing to step S81.

If it is determined that the second energization processing isterminated (S92: YES), the CPU 90 turns off the energization of theexhaust drain valve 68 (S93), then turns off the energization of theexhaust drain valve 69 (S94), and terminates the second energizationprocessing.

According to the present embodiment, in the case where the temperaturesTf and Tg are 5° C. or higher which is not a freezing condition, it isnot necessary to heat any of the exhaust drain valves 68 and 69, andtherefore both of the valves are maintained to be in the state ofenergization off.

In the case where the temperature Tf of the exhaust drain valve 69 islower than 5° C., first, the exhaust drain valve 69 is energized to beheated while the exhaust drain valve 68 is in the state of energizationoff. In the case where the temperature Tf continues to be lower than 5°C., the energization of the exhaust drain valve 69 is maintained whenthe temperature Tg of the exhaust drain valve 68 is 5° C. or higher.Thus, the exhaust drain valve 69 may remain energized until it is warmedup. In the case where the temperature Tg of the exhaust drain valve 68is lower than 5° C., the energization of the exhaust drain valve 69 isturned off, and the exhaust drain valve 68 is energized to be heated. Inthis case also, the gas that has flown through the exhaust drain valve68 warms up the exhaust drain valve 69.

In the present embodiment, the temperature sensor is provided at both ofthe valves on the upstream side and downstream side in the gas and waterdischarging direction, so that the valve on the downstream side that iseasily frozen is energized first and heated.

As described above, in a fuel cell according to the present disclosurecomprising a power generation unit configured to generate electricity byreacting hydrogen and oxygen, a solenoid valve discharging gas or wateremitted from the power generation unit to the outside, and a controlunit configured to control energization of the solenoid valve, aplurality of the solenoid valves are aligned along a direction in whichthe gas or the water is discharged, a temperature detection unit isprovided that detects the temperature of a solenoid valve on thedownstream side in the discharging direction, and if the temperature ofthe solenoid valve is equal to or lower than a predetermined value, thecontrol unit energizes a solenoid valve on a more upstream side in thedischarging direction than the solenoid valve and closes at least one ofthe other solenoid valves aligned with the energized solenoid valve.

In the present disclosure, the temperature detection unit is providedonly at the solenoid valve on the downstream side in the gas or waterdischarging direction, so that the solenoid valve on the upstream sidewhere no temperature detection unit is provided is energized first andheated. If the solenoid valve where the temperature detection unit isprovided is heated first, the temperature of the solenoid valve where notemperature detection unit is provided may be lowered, which may freezethe solenoid valve. If the solenoid valve on the upstream side isheated, the heated gas or water flows through the solenoid valve on thedownstream side while heating the solenoid valve on the downstream side.

Since at least one of the aligned solenoid valves is closed, there is norisk of a hydrogen leak.

Thus, power generation may favorably be performed.

In a fuel cell according to the present disclosure comprising: a powergeneration unit configured to generate electricity by reacting hydrogenand oxygen; a solenoid valve for discharging gas or water emitted fromthe power generation unit to the outside; and a control unit configuredto control energization of the solenoid valve, a plurality of thesolenoid valves are aligned along a direction in which the gas or thewater is discharged, a plurality of temperature detection unitsconfigured to detect the temperature of each solenoid valve is provided,and if the temperature of a solenoid valve on the downstream side in thedischarging direction is equal to or lower than the first predeterminedvalue, the control unit energizes the solenoid valve and closes at leastone of the other solenoid valves aligned with the energized solenoidvalve.

In the present disclosure, the temperature detection unit is provided atboth of the solenoid valves on the upstream side and downstream side inthe gas and water discharging direction, so that the solenoid valve onthe downstream side that is easily frozen is energized first and heated.

This may favorably prevent freezing. The temperature of each solenoidvalve is then detected and a solenoid valve is energized as needed,which prevents supply of unnecessary electricity.

At least one of the aligned solenoid valves is closed, therebyeliminating the risk of a hydrogen leak.

Thus, power generation may favorably be performed.

In the fuel cell according to the present disclosure described above, inthe case where the solenoid valve is energized, the control unitcontinues energization if the temperature of the solenoid valve is equalto or lower than the first predetermined value and the temperature of asolenoid valve on a more upstream side in the discharging direction thanthe energized solenoid valve is equal to or higher than the secondpredetermined value.

According to an aspect of the present disclosure, in the case where thetemperature of a solenoid valve on the downstream side in thedischarging direction is equal to or lower than the first predeterminedvalue and the temperature of a solenoid valve on a more upstream side inthe discharging direction than the solenoid valve on the downstream sideis equal to or higher than the second predetermined value and thus norisk of the solenoid valve on the upstream side being frozen is present,the solenoid valve on the downstream side continues being energized soas to favorably prevent it from being frozen.

In the fuel cell as described above, the control unit switches asolenoid valve to be energized if a predetermined time elapses.

According to an aspect of the present disclosure, a solenoid valve isswitched so that a solenoid valve not being energized may be heated toprevent it from being frozen. The solenoid valve that has been energizedis closed by stopping energization thereof, which may prevent a hydrogenleak.

In the fuel cell according to an aspect of the present disclosure asdescribed above, in the case of performing the energization processing,the control unit supplies current having the same polarity as that ofthe drive current in the energization processing at the time ofdischarging the gas or the water to the outside to the solenoid valve.

According to an aspect of the present disclosure, no special solenoidvalve is necessary and regular drive current allows the solenoid valveto operate, eliminating the need for a special electric circuit.

In the fuel cell according to the present disclosure as described above,in the case of terminating the energization processing, the control unitcloses the solenoid valves in sequence from the upstream side in thedischarging direction.

According to an aspect of the present disclosure, no pressure remainsbetween solenoid valves, which favorably prevents a hydrogen leak.Moreover, moisture is unlikely to remain as well, which favorablyprevents freezing.

In the fuel cell according to an aspect of the present disclosure, thesolenoid valve is covered with a heat insulating material.

According to an aspect of the present disclosure, the heat insulatingmaterial may retain the heat generated by energizing the solenoid valve,which more favorably prevents freezing.

A control method according to the present disclosure for a fuel cellcomprising: a power generation unit configured to generate electricityby reacting hydrogen and oxygen; a plurality of aligned solenoid valvesfor discharging gas or water emitted from the power generation unit tothe outside; a control unit configured to control energization of thesolenoid valve; and a temperature detection unit configured to detectthe temperature of a solenoid valve on a downstream side in thedischarging direction, comprises detecting the temperature of thesolenoid valve, and if the temperature of the solenoid valve is equal toor lower than a predetermined value, energizing a solenoid valve on amore upstream side in the discharging direction than the solenoid valveon the downstream side and closing at least one of the other solenoidvalves aligned with the energized solenoid valve.

In the present disclosure, the temperature detection unit is providedonly at the solenoid valve on the downstream side, so that the solenoidvalve on the upstream side where no temperature detection unit isprovided is energized first and heated. If the solenoid valve on theupstream side is heated, the heated gas or water flows through a valveon the downstream side while heating the solenoid valve on thedownstream side.

Since at least one of the aligned solenoid valves is closed, there is norisk of a hydrogen leak.

Thus, power generation may favorably be performed.

A control method according to the present disclosure for a fuel cellcomprising: a power generation unit configured to generate electricityby reacting hydrogen and oxygen; a plurality of aligned solenoid valvesfor discharging gas or water emitted from the power generation unit tothe outside; a control unit configured to control energization of thesolenoid valve; and a plurality of temperature detection unitsconfigured to detect the temperatures of solenoid valves respectively,comprises: detecting the temperature of the solenoid valve, and if thetemperature of the solenoid valve on a downstream side in thedischarging direction is equal to or lower than a first predeterminedvalue, energizing the solenoid valve and closing at least one of theother solenoid valves aligned with the energized solenoid valve.

In the present disclosure, the temperature detection unit is provided ateach of the solenoid valves on the upstream side and downstream side inthe gas and water discharging direction, so that the solenoid valve onthe downstream side that may easily be frozen is energized first andheated. This may favorably prevent freezing. The temperature of eachsolenoid valve is then detected and a solenoid valve is energized asneeded, which prevents supply of unnecessary electricity.

Since at least one of the aligned solenoid valves is closed, there is norisk of a hydrogen leak.

Thus, power generation may favorably be performed.

A non-transitory computer readable recording medium according to thepresent disclosure records a computer program causing a computerconfigured to control a fuel cell comprising: a power generation unitconfigured to generate electricity by reacting hydrogen and oxygen; aplurality of aligned solenoid valves for discharging gas or wateremitted from the power generation unit to the outside; a control unitconfigured to control energization of the solenoid valve; and atemperature detection unit configured to detect the temperature of asolenoid valve on a downstream side in the discharging direction, toexecute processing of: obtaining the temperature of the solenoid valve;determining whether or not the temperature of the solenoid valve isequal to or lower than a predetermined value; and if it is determinedthat the temperature of the solenoid valve is equal to or lower than thepredetermined value, energizing a solenoid valve on a more upstream sidein the discharging direction than the solenoid valve on the downstreamside and closing at least one of the other solenoid valves aligned withthe energized solenoid valve.

In the present disclosure, the temperature detection unit is providedonly at the solenoid valve on the downstream side, so that the solenoidvalve on the upstream side where no temperature detection unit isprovided is energized first and heated. If the solenoid valve on theupstream side is heated, the heated gas or water flows through a valveon the downstream side while heating the solenoid valve on thedownstream side.

At least one of the aligned solenoid valves is closed, therebyeliminating the risk of a hydrogen leak.

Thus, power generation may favorably be performed.

A non-transitory computer readable recording medium according to thepresent disclosure records a computer program causing a computerconfigured to control a fuel cell provided with: a power generation unitconfigured to generate electricity by reacting hydrogen and oxygen; aplurality of aligned solenoid valves for discharging gas or wateremitted from the power generation unit to the outside; a control unitconfigured to control energization of the solenoid valve; and aplurality of temperature detection units configured to detect thetemperature of each solenoid valve, to execute processing of: obtainingtemperatures of the solenoid valves respectively; determining whether ornot a temperature of a solenoid valve on the downstream side in thedischarging direction is equal to or lower than a first predeterminedvalue; and outputting, if it is determined that the temperature of thesolenoid valve is equal to or lower than the first predetermined value,a command to energize the solenoid valve and to close at least one ofthe other solenoid valves aligned with the energized solenoid valve.

In the present disclosure, the temperature detection unit is provided atboth of the solenoid valves on the upstream side and downstream side inthe gas and water discharging direction, so that the solenoid valve onthe downstream side that is easily frozen is energized first and heated.This may favorably prevent freezing. The temperature of each solenoidvalve is then detected and a solenoid valve is energized as needed,which prevents supply of unnecessary electricity.

At least one of the aligned solenoid valves is closed, therebyeliminating the risk of a hydrogen leak.

Thus, power generation may favorably be performed.

The present invention is not limited to the contents of Embodiments 1and 4 described above, but various modifications can be made within thescope defined by the appended claims. That is, embodiments to beobtained by combining technical measures obtained from suitablemodifications within the scope defined by the claims are also includedin the technical scope of the present invention.

For example, the number of solenoid valves aligned in the water or gasdischarging direction is not limited to two but may also be three ormore. It is however necessary to close at least one of the alignedsolenoid valves.

Furthermore, the arrangement of solenoid valves is not limited to thecase where multiple solenoid valves are aligned both on the gasdischarging side and the water discharging side, but another case mayalso be employed where solenoid valves are aligned on either one of thedischarging sides.

It is to be noted that, as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise.

What is claimed is:
 1. A fuel cell system comprising a power generationunit configured to generate electricity by reacting hydrogen and oxygen,a plurality of solenoid valves for discharging gas or water emitted fromthe power generation unit to an outside, a drainage; an exhaust passage;a hydrogen supply unit supplying the hydrogen to the power generationunit; a heating source heating the hydrogen supply unit; a hydrogensupply passage through which the hydrogen flows from the hydrogen supplyunit to the power generation unit; and a control unit configured tocontrol energization of the solenoid valves, wherein the solenoid valvesare aligned along a discharging direction in which the gas or the wateris discharged, the solenoid valves are arranged in series in thedrainage or the exhaust passage, the fuel cell system further comprisesa plurality of temperature detection units configured to detecttemperatures of the solenoid valves respectively, and in a case where atemperature of a solenoid valve on a downstream side in the dischargingdirection is equal to or lower than a first predetermined value, thecontrol unit energizes the solenoid valve and closes at least one ofother solenoid valves aligned with the solenoid valve that is energized.2. The fuel cell system according to claim 1, wherein, in a case wherethe solenoid valve is being energized, the control unit continuesenergization when the temperature of the solenoid valve is equal to orlower than a first predetermined value and the temperature of a solenoidvalve on a more upstream side in the discharging direction than thesolenoid valve that is being energized is equal to or higher than asecond predetermined value.
 3. The fuel cell system according to claim1, wherein the control unit switches the solenoid valve to be energizedin a case where a predetermined time elapses.
 4. The fuel cell systemaccording to claim 1, wherein, in a case of performing the energizationprocessing, the control unit supplies, to the solenoid valve, currenthaving a same polarity as a polarity of drive current in energizationprocessing performed at the time of discharging the gas or the water tothe outside.
 5. The fuel cell system according to claim 1, wherein, in acase of terminating the energization processing, the control unit closesthe solenoid valves in sequence from a solenoid valve on an upstreamside in the discharging direction.
 6. The fuel cell system according toclaim 1, wherein the solenoid valve is covered with a heat insulatingmaterial.
 7. A control method for a fuel cell system comprising: a powergeneration unit configured to generate electricity by reacting hydrogenand oxygen; a plurality of aligned solenoid valves for discharging gasor water emitted from the power generation unit to an outside; adrainage; an exhaust passage; a hydrogen supply unit supplying thehydrogen to the power generation unit; a heating source heating thehydrogen supply unit; a hydrogen supply passage through which thehydrogen flows from the hydrogen supply unit to the power generationunit; a control unit configured to control energization of the solenoidvalve; and a plurality of temperature detection units configured todetect temperatures of the solenoid valves respectively, wherein thesolenoid valves are arranged in series in the drainage or the exhaustpassage, the method comprising: detecting temperatures of the solenoidvalves, respectively, and in a case where a temperature of a solenoidvalve on a downstream side in a discharging direction is equal to orlower than a first predetermined value, energizing the solenoid valveand closing at least one of other solenoid valves aligned with thesolenoid valve that is energized.
 8. A non-transitory computer readablerecording medium with a computer program for causing a control unit tocontrol a fuel cell system comprising: a power generation unitconfigured to generate electricity by reacting hydrogen and oxygen; aplurality of aligned solenoid valves for discharging gas or wateremitted from the power generation unit to an outside; a drainage; anexhaust passage; a hydrogen supply unit supplying the hydrogen to thepower generation unit; a heating source heating the hydrogen supplyunit; a hydrogen supply passage through which the hydrogen flows fromthe hydrogen supply unit to the power generation unit; the control unitconfigured to control energization of the solenoid valves; and aplurality of temperature detection units configured to detecttemperatures of solenoid valves respectively, wherein the solenoidvalves are arranged in series in the drainage or the exhaust passage,the computer program causing the control unit to execute processing of:obtaining temperatures of the solenoid valves respectively; determiningwhether or not a temperature of a solenoid valve on a downstream side ina discharging direction is equal to or lower than a predetermined value;and outputting, in a case where it is determined that the temperature ofthe solenoid valve is equal to or lower than the first predeterminedvalue, a command to energize the solenoid valve and to close at leastone of other solenoid valves aligned with the solenoid valve that isenergized.